DESCRIPTION: (provided by the applicant): The goal of this project is to study the surface glycoproteins of the African trypanosome, Trypanosoma brucei. The variant surface glycoprotein (VSG) of bloodstream form parasites protects subsurface structures from recognition by the host immune system. Switching expression from one VSG to another (antigenic variation) allows the parasite to survive in the host's bloodstream. Procyclin is the unusual protein that covers the surface of the insect form of T. brucei. Our studies focus mainly on the glycosyl groups of these proteins, especially the GPI anchors. The VSG GPI is unusual in that it contains the fatty acid myristate. Because trypanosomes have massive amounts of VSG they need large amounts of myristate, which is a rare fatty acid in the host's bloodstream. In fact, it appeared that there was not enough myristate in the serum to provide sufficient myristate for GPI anchors. Only recently our lab found that trypanosomes actually synthesize myristate, overturning the 30-year-old belief that they cannot make fatty acids. The first specific aim is to study the mechanism of myristate synthesis. Although trypanosomes are eukaryotes, the fatty acid synthetic machinery resembles that of prokaryotes. Of special importance will be studies aimed at testing inhibitors of fatty acid synthesis as candidate anti-trypanosomal drugs. The second specific aim concerns the mechanism of GPI anchoring and protein glycosylation. Previous studies along these lines have been biochemical, but the proposed approach involves genetics. These studies will involve the powerful new technique of RNA interference (RNAi) that selectively silences trypanosome genes. The third aim involves the mechanism of GPI myristoylation, by remodeling reactions. These experiments involve attempts to purify and study a myristoyl transferase, using biochemical and genetic techniques.